The invention relates to quick load binding systems for securing and maintaining loads to a truck having an open flat bed surface.
During road shipping of goods on an open flat-bed trailer, a strap tightening system is requiredxe2x80x94and is compulsory under government regulationsxe2x80x94to maintain the load in place over the trailer flat-bed. Loads on open trailers can be conventionally held in place by wrap-around straps, extending transversely over the load and spaced from one another in a fore and aft direction. Each of these straps is tightened in place by a corresponding winch. However, due to the road bumps, there is a tendency for the load distribution to shift during road travel, and therefore, the transverse wrap-around straps become loosened, so that the strap tensioning force applied on the load becomes insufficient. Periodically after each half hour or so, the truck driver must pull his truck on the side of the road and stop his truck, get out and manually tighten with an elongated one-meter long lever bar once again the flexible strap with a winch. Typically, the applied tensioning load will be about two metric tons for each 10 centimeters wide straps. The lever bar engages through a bore at the free end of the winch shaft.
Such a conventional load tightening system is physically demanding for the truck driver, with eventual back pain injuries that can follow after a while. It is inconvenient for the truck driver, when the weather is bad: heavy rain, ice or snow. During road travel, it generates anxiety with the truck driver, as the latter is never sure when exactly the load needs to be re-tightened; also it may take some time before the next upcoming suitable road side space becomes available for temporarily parking the trailer to check the tightening of the load, thus again generating nervousness in the truck driver never knowing if part of his load will accidentally release the flat-bed of his trailer and undesirably fall down onto the road, before he can reach the next upcoming curbside road park space. Morever, such a load tightening system does constitute a safety hazard for both this truck driver and incoming motorists, because he has to work on the side of the road, sometimes at night, with an elongated bar projecting away from the truck and across the road where incoming motorists may not see the truck driver. Also, such a load tightening system is unreliable since it does not enable the truck driver to uniformly adjust the proper tensioning for each and every strap during road travel. Also, because there are usually around twelve (12) such transverse straps and strap tensioners on a typical flat bed open trailer, and the truck driver needs to crank each strap winch individually, load tightening is a tiresome and lengthy business.
An object of this invention is to enhance operational safety of flat bed open trailers.
Another object of this invention is to tighten in a single operation all strap winches of a flat bed trailer.
Another object of the present invention is to increase efficiency of operation of flat bed open trailers.
Another object of this invention is to reduce the likelihood of work related bodily injuries by truck drivers.
In accordance with the objects of the invention, there is disclosed a strap winch device assembly for fitting to a truck trailer, to periodically tighten the load supported by the open trailer. This load tightening can be performed either automatically, at set intervals (for example regular intervals), or remotely by the truck driver without having to leave his driving cabin. A number of these winch devices are connected to a single fore and aft drive shaft, which is rotatably carried by and extends along the side of the trailer. The drive shaft is driven by a motor to tighten any straps that loosen when the trailer is in motion over the road. Trailer load distribution typically shifts during road travel, due to road-induced vibrations.
More particularly, the present invention introduces a pneumatic system for automaticallyxe2x80x94or by remote controlxe2x80x94providing tightening load on the wrap-around straps, so that the trucker does not need to periodically stop on the side of the road, and get out of his cab, to manually re-tighten his load with the straps. To the winch cable tightening system, there is added an elongated shaft which extends along the side of the full length of the trailer, and which drivingly engages a pneumatic motor at the front end of the trailer. This motor is periodically activated during road travel, for short durations each time. This can be done either automatically, at set intervals, or by remote control, at the discretion of the truck driver inside his cab. Upon reaching shipping destination, some of these cable tightening assemblies corresponding to the registering load units to be unloaded, are released manually by a clutch release handle.
This strap tensioning system includes an integral tension limiter, that constantly maintains the tension on the load-tightening straps, contrarily to conventional manual load tightening systems. The automatic tightening system operates thanks to a safety ratchet member, including a locking pawl, to maintain the tightening load without having to continuously maintain in operation the drive motor.
The tightening system mechanism includes three different gear wheels. One gear wheel is located on the drive shaft, the second gear wheel is located on the drum, and the third and last gear wheel interconnects the first and second gear wheels. The third gear wheel is provided with a spring biased system which becomes inoperative when the required tensioning force is reached. This same gear wheel also enables the user to deactivate the drum of the drive shaft with the clutch release arm, to alternately enable a manual operation or the dismantling of the straps.
Also, the strap tensioning devices are slidingly mounted along the elongated motor shaft, so that their relative fore and aft position along the trailer flat bed can be adjusted to fit any type of load. The transmission shaft is for example cross-sectionally hexagonal, but other suitable shapes, most preferably polygonal, or other configurations, e.g. a knurled surface on an otherwise cylindroid shaft, could be used provided they allow transmission of power from the motor to the tightening devices.
More particularly, the invention relates to a strap tightening system for use in securing a load with a wrap-around strap over a flat bed open trailer, said system comprising:
at least one strap tensioning unit, including: a) a main frame, to be mounted to the trailer; b) a strap winding member, rotatably mounted to said main open frame and lockingly engageable by one end portion of the strap; c) a gear assembly, rotatably mounted to said main open frame; a motor, to be mounted to the trailer at a distance from said tensioning unit and to be connected to a power supply;
a drive shaft, operatively interconnecting said tensioning unit gear assembly and said motor, said drive shaft bringing said strap winding member to rotate upon actuation of said motor;
a clutch assembly, operatively interconnecting said gear assembly and said cable winding member, wherein upon the load applied by the tightening strap onto said cable winding member exceeding a set threshold, said clutch assembly disconnects said gear assembly from said cable winding member.
A manual clutch release member may be added, for manually disconnecting said gear assembly from said cable winding member. A manual strap tightening device could also be added, being associated with said strap winding member, for tightening said strap independently of said drive shaft. A rail member could also be added, said rail member including a first portion, to be anchored to the trailer flat bed in a fore and aft direction, and a second portion, slidingly retaining said strap tensioning unit open frame, wherein the relative position of said strap tensioning unit device can be slidingly adjusted along the length of the trailer in accordance with the relative position on the trailer bed of the load to be secured.
It would also be envisioned to add a safety ratchet and pawl assembly, mounted to said main frame and cooperating with said strap winding member, said safety ratchet and pawl assembly preventing said strap winding member from unwinding once said motor is deactivated.
There may be at least a few strap tensioning units, and preferably between eight and fourteen (8-14), located spacedly from one another and adjustable movable relative to one another along said rail member.
The invention also relates to the combination of the open trailer per se and the strap tightening unit.
The invention also relates to a method of securing a load on a flat bed trailer with at least one strap tightening unit, the strap tensioning unit of the type having a main frame, to be mounted to the trailer, a strap winding member, rotatably mounted to the main open frame and lockingly engageable by one end portion of the strap, a gear assembly, rotatably mounted to said main open frame, and a clutch assembly, operatively interconnecting said gear assembly and said cable winding member; wherein said method comprises the following steps: a) extending the strap transversely over a selected portion of the trailer load carrying bed; b) engaging an inner end portion of the strap around said strap winding member; c) applying a rotational force on said strap winding member to tighten said strap against the load on the trailer bed; d) allowing said clutch assembly to disconnect said gear assembly from said cable winding member, once the load applied by the tightening strap onto said cable winding member exceeds a set threshold; e) locking said cable winding member at its threshold load with a lock member; f) releasing said rotational force on said strap winding member.
The following additional step (aa) could intervene before said step (a): adjusting the position of said strap tensioning unit along the trailer, to register with the load on the trailer bed. Also, there could be a number of such said strap tensioning units; so that the following additional step would be involved in this method, intervening between said steps (aa) and (a): adjusting the position of the other said strap tensioning units relative to one another, to adapt to the load distribution on the trailer bed.
The invention also relates to a load tightening device for use in securing a load with a wrap-around flexible strap over a flat bed trailer, said device comprising: a main rigid frame, to be anchored to the trailer; a winding member, rotatably mounted to said main frame and to be connected to the load securing strap for winding the latter; power means, for power operating said winding member to wind the strap; power transmission means, operatively interconnecting said winding member and said power means; clutch means, deactivating said power transmission means once the torque applied by the tightening strap onto said strap winding member exceeds a set threshold and said strap winding member reaches a threshold winded state; and lock means, maintaining said strap winding member in its threshold winded state once said power means is deactivated.
Said gear assembly could include a ring gear, a drive gear integral to said drive shaft and intermeshing with said ring gear; and wherein said clutch assembly includes a clutch casing, mounted radially inward of said ring gear, said clutch casing including a number of radial recessses, a biasing member fully engaged into each of said radial recesses, and a bearing member mounted into each of said radial recesses radially outwardly of said biasing member, said ring gear defining a radially inner edge portion having a number of cavities in register with corresponding said radial recesses, each of said ring gear cavities sized to complementarily accommodate a fraction of a corresponding bearing member, each said bearing member biased by a corresponding one of said biasing members radially outwardly toward and against a corresponding one of said ring gear cavities, said set load threshold being a function of said biasing member.
There could also be added load adjusting set screws, each of said set screws mounted into a corresponding one of said radial recesses radially inwardly of said biasing member, said set screws enabling an operator to manually adjust said set load threshold.
Preferably, the range of said set load threshold is between about 1360 and 2270 kg, most preferably of about 1810 kg.